Polymer Chemistry Chapter 10 Quiz
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Questions and Answers

What are the two general classes of polymers?

  • Amorphous and crystalline
  • Thermoplastics and thermosets (correct)
  • Linear and branched
  • Addition and condensation

    • What happens to the melting point as molecular weight increases?

    increases

    As the degree of branching increases, what happens to density?

    decreases

    What is a plastic that has two monomers in its molecular structure called?

    <p>dimer</p> Signup and view all the answers

    A polymer in which the chains are highly ordered is said to be:

    <p>crystalline</p> Signup and view all the answers

    What is the term for a polymer with essentially random chain arrangement?

    <p>amorphous</p> Signup and view all the answers

    The stiffer HDPE is associated with what kind of molecular weight?

    <p>higher</p> Signup and view all the answers

    What is the molecular structural difference between HDPE, LDPE, and LLDPE?

    <p>HDPE has linear chains, LDPE has highly branched chains, and LLDPE has short, branched chains.</p> Signup and view all the answers

    What is the process of improving properties of plastic film by stretching in one or two directions called?

    <p>Orientation</p> Signup and view all the answers

    LLDPE stands for?

    <p>linear low-density polyethylene</p> Signup and view all the answers

    PP stands for?

    <p>polypropylene</p> Signup and view all the answers

    PS stands for?

    <p>polystyrene</p> Signup and view all the answers

    PVC stands for?

    <p>polyvinyl chloride</p> Signup and view all the answers

    EVOH stands for?

    <p>ethylene-vinyl alcohol</p> Signup and view all the answers

    PA stands for?

    <p>polyamide</p> Signup and view all the answers

    PET stands for?

    <p>polyethylene terephthalate</p> Signup and view all the answers

    PVDC stands for?

    <p>polyvinylidene chloride</p> Signup and view all the answers

    OPP stands for?

    <p>oriented polypropylene</p> Signup and view all the answers

    PVAC stands for?

    <p>polyvinyl acetate</p> Signup and view all the answers

    What is a distinguishing feature of a polymer with lower crystallinity compared to one with higher crystallinity?

    <p>better clarity</p> Signup and view all the answers

    How do the general properties of thermoplastics and thermosets differ?

    <p>Thermosets have higher potential use temperatures and resistance to solvents.</p> Signup and view all the answers

    What properties of plastics are affected by the molecule's degree of polarity?

    <p>melting point, solubility, barrier properties, coefficient of friction</p> Signup and view all the answers

    How are heat-shrink properties imparted to a polymer?

    <p>Using a combination of thermal and mechanical history to produce shrink film.</p> Signup and view all the answers

    What is cold flow?

    <p>Deformation of plastics under load, also referred to as 'creep'.</p> Signup and view all the answers

    Why are all plastics clear in the melt state?

    <p>Due to rapid molecular movement that prevents ordering of molecules.</p> Signup and view all the answers

    Which two common packaging plastics are predominantly nonpolar?

    <p>polyethylene and polypropylene</p> Signup and view all the answers

    From what raw material source are most packaging plastics made?

    <p>petrochemicals</p> Signup and view all the answers

    What is the purpose of flame or corona treatment?

    <p>To impart polarity to the surface of low-polarity plastics.</p> Signup and view all the answers

    Which has the higher melting point: high-molecular-weight polysulfone or low-molecular-weight polysulfone?

    <p>High-molecular-weight polysulfone</p> Signup and view all the answers

    What is the purpose and advantage of producing copolymers?

    <p>To bring together favorable properties of distinctly different polymers.</p> Signup and view all the answers

    Study Notes

    Polymer Classes

    • Two main types of polymers: thermoplastics and thermosets.
    • Thermoplastics are widely used in packaging; they can reshape upon heating.
    • Thermosets have cross-linked structures and remain fixed once set, unable to be reshaped.

    Molecular Weight and Properties

    • As molecular weight increases, melting point also increases.
    • Higher molecular weight in HDPE results in increased stiffness.

    Structural Characteristics

    • Increased branching in polymer molecular structure leads to decreased density.
    • HDPE features linear chains, while LDPE has highly branched chains, and LLDPE possesses short, branched chains.

    Polymer Conformation

    • Polymers can be crystalline with ordered chains, or amorphous with random arrangements.
    • Crystalline polymers tend to have higher density and lower clarity compared to amorphous types.

    Orientation and Stretching

    • Orientation of polymer molecules through stretching enhances properties by aligning them along the stress direction.

    Common Polymers and Their Acronyms

    • LLDPE: Linear low-density polyethylene
    • PP: Polypropylene
    • PS: Polystyrene
    • PVC: Polyvinyl chloride
    • EVOH: Ethylene-vinyl alcohol
    • PA: Polyamide
    • PET: Polyethylene terephthalate
    • PVDC: Polyvinylidene chloride
    • OPP: Oriented polypropylene
    • PVAC: Polyvinyl acetate

    Physical Properties and Applications

    • Clarity is generally lower in more crystalline polymers compared to amorphous ones.
    • Thermosets are designed for higher use temperatures and solvent resistance.

    Influence of Polarity

    • Polarity affects melting point, solubility, barrier properties, and coefficient of friction in plastics.

    Heat and Cold Flow

    • Heat-shrink properties are developed through specific thermal and mechanical processing.
    • Cold flow, or "creep," is crucial in applications where plastics bear significant loads.

    Behavior in Melt State

    • All plastics appear clear in their melt state due to the rapid motion of molecules, preventing any structured arrangement.

    Material Sources

    • The majority of packaging plastics originate from petrochemical sources.
    • Common packaging plastics like polyethylene and polypropylene are predominantly nonpolar.

    Surface Treatment

    • Flame or corona treatment enhances surface polarity, improving adhesion properties for low-polarity plastics.

    Melting Points of Polymers

    • High molecular weight polysulfone exhibits a higher melting point compared to lower molecular weight counterparts.

    Copolymers

    • Copolymers combine the beneficial properties of different polymers, allowing for improved material performance.

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    Description

    Test your understanding of polymer chemistry as presented in Chapter 10. This quiz focuses on the two main classes of polymers, their applications in packaging, and their molecular structures. Perfect for nonchemists looking to deepen their knowledge in this area.

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